Method of manufacturing lead carbonates.



. Illinois, both citizens of v of lead carbonates and and I'dilute the paste thus No Drawing.

JOHN SGHAEFFER, OF J'OPLIN,

RATION OF MISSOURI.

To all whom it may concern I I Be it lmown that we, JOHN A. SoHAnrrER, residing in the city of Joplin, in the county of Jasper and State of Missouri, and JOHN R. MACGREGOR residing in the city of Chicago, in the county of Cook and State of the-United States of America, have invented certain new and useful Improvements in Methods of Manufacturing Lead Carbonates, of which the following isa true and exact description.

My invention relates to the manufacture particularly of the basic lead, carbonate for use as a pigment, and it is based on my litharge, the product made by converting litharge into a fume by heat, in admixture with water will be converted into lead carbonate, either basic or neutral in accordance with thelength of the treatment, by treating the mixture with carbon dioxid gas, and on my further discovery that the process is greatly hastened by having acetic acid in solution in the water. I

In carrying my process into effect in the best way known to me I triturate the fumed litharge with water to break up any lumps formed with water and I add acetic acid to the mixture in quantity of about, ten per cent. of the litharge, which acid is of course dissolved in the water. I then pass a stream of purified carbon dioxid gas into the mixture, the gas being thoroughly distributed in the mixture by any convenient means. this treatment the color of the mixture,

which is originally of a canary yellow color,

changes gradually but promptly, first to lighter yellows andfinally to a white which indicates thatthe lead oxid has been changed to basic carbonate of 1 lead. While the change in color is taking place there is also a change in the -physical structure of the material, the pigment in suspension becoming more flocculent and the mixture thicker.

The pigment appears to be most flocculent I when the basic lead carbonate formed corresponds to the. formula 2PbCO,Pb(OH) which is the accepted formula for basic lead carbonate of best quality made by the old Dutch method, and I prefer to stop the treatment when this composition is attained,

both because it is I believe the best for use as-a pigment and also because it is advisable MISSOURI, rumors, ASSIGNORS 'ro 210mm LEAD oomrm, or JOPLIN, mrssoum, A coaro- METHOD OF MANUFACTURING LEAD CARBON ATES.

Specification of Letters Patent.

discovery that fumed As a result of,

AND JOHN MAOGREGOR, OF CHICAGO,

' Patented Nov. a, rare.

. Application filed May 2,1916. Serial No. 94,883.

that the pigment should have the same oil requirement for grinding as the product made by the old Dutch process. The treatment' with carbon dioxid gas can 'be contmued with the result of forming less basic lead carbonates and finally a neutral carbonate, but I have found" no advantage in contmuing the treatment beyond the point indicated which can be ascertained roughly by the flocculence of the suspended pigment. but preferably by treatment continues. continued until the pigment is secured After the reaction has desired composition of the supply of gas is v stopped, the solid pigment is removed from .the mother liquor, carefully washed and partially dried in a filter press. The resultant moist basic carbonate of lead is then ground in oil. The mother liquor I use and reuse in the treatment of further quantities of fumed litharge until it is used up. In practime I have used for my initial mixture 100 parts of fumed litharge to about 400 parts of water and 10 parts of acetic acid. Where acetic acid is used in solution in the water a cyclical reaction takes duction of the lead carbonate of desired composition is much more rapid than where no acid is used. The cyclical reaction I have referred to takes place in that the acetic acid combines with a litharge forming a lead acetate which is promptly acted upon by the carbon dioxid, forming basic lead carbonate and liberating the acetic acid to act on further quantities of fumed litharge.

Itwill be understood that my process differs from other so. calledquick methods of making basic lead carbonate in that it starts with and operates upon a very reactive material, fumed litharge, which is held in sus- 95 pension, not in solution in water. Where I use acetic acid in solution in the water there is of course a slight solution of the fumed litharge to permit the cyclical reaction to take'place, but there is nothing comparable 100 with the complete formation of lead acetate .Which 'is characteristic of the older quick processes.

bonate which consists in mixing fumed lithtesting samples as the 65 place and the proportion of the fumed and desire to secure by arge with water and treating the mixture lead carbonate which consists in mixing with carbon dioxid gas. fumed litharge in water having acetic acid 1) 2. The method of manufacturing lead insolution, treating the mixture with carbon carbonate which consists in mixing fumed dioxid gas andstopping the gas treatment 5 litharge in water having acetic acid in soluwhen the basic lead carbonate formed has tion and treating the mixture with carbon the desired composition.

JOHN A. SGHAEFFER,

dioxid gas.

3. The method of manufacturing basic JOHN R. MACGREG-OR. 

